The US Defense Advanced Research Project Agency (DARPA) is working on robotic in-orbit services for satellites in GEO. Last September, at DARPA's "Wait! What?" symposium in St. Louis, Missouri, Pam Melroy​ outlined the idea, fittingly titled "Port of Call at 36,000 KM, explaining that it will happen in geosynchronous orbit and asking:

What if you could build a satellite up there in GEO? What if you can repair it? What if you could upgrade it with the latest electronics?

Melroy, who as a NASA astronaut piloted two space shuttle missions, is intimately familiar with one of the foundations of DARPA's GEO Robotic Service (GRS) platform: the robotic arm. Both of her shuttle trips involved additions to the International Space Station in which the arm was used.

The ISS arm also has been used in repairing the Hubble Telescope five times.

But that was at 347 miles aloft, in low Earth (LEO) orbit.

GEO presents other issues, requiring greater capabilities.

For example, the arm would have to include more automation and safety features. The last thing anybody wants is a malfunction that can knock out a satellite or create debris in GEO. As Melroy, now deputy director of the agency's Tactical Technology Office. added:

(DARPA's arm has) interesting characteristics, like robot reflexes and compliance control to greatly minimize the risk of debris from inadvertent collisions.

The platform would be more than just a one-stop shop for satellites in GEO orbit, though. It would be a part of an entire infrastructure geared toward robotic in-orbit services.

We think this is a critical capability toward building a transportation hub that allows transportation to and from the Earth's surface, from LEO orbit to GEO and even beyond the Earth's orbit. We think that these capabilities are not just about a single monolithic satellite with a few capabilities, but instead are about a vibrant, robust ecosystem that involves transportation, repair, refueling, upgrading, in situ construction.

Just look at the great seafaring port cities in the world for inspiration and imagine a port of call at 36,000 kilometers and you will understand what it is she envisions.

The majority of satellites operating in geosynchronous orbit are commercially owned and operated, so last year DARPA called upon companies like Intelsat General - which has done research on the idea for many years - for technical help and security advice in a Request for Information. Basically, the RFI sought insight into such things as potential tools that would be needed on a robotic arm in future GEO service.

DARPA also wanted to know what modifications might be needed in existing orbiting satellites to make them serviceable.

Gordon Roesler, a DARPA program manager specializing in space robotics, said in a news release.:

We're asking the space community to think hard about how they want the future of space operations and how GEO robotics could help. Their insights are essential as we take the first concrete steps toward viable satellite-servicing capabilities in GEO. If we're successful, we will significantly accelerate development of a capacity to maximize the utility of current space infrastructure and enhance the capabilities of future systems.

DARPA is not just concerned about the technical aspects, though. They are also seeking advice in formulating a business case that would make the GRS platform financially feasible. A "fee-for-service" arrangement with military and commercial users is just one option they have discussed.

As Roesler said:​

Creating a public-private partnership is an innovative way to ensure that GEO robotic servicing gets community buy-in to succeed long term. Strategic partnership with commercial firms will be pursued in areas that both stabilize costs and improve the resilience of space architectures on which we rely.

DARPA's Phoenix Program

Another is "satlets" -- an idea in which production-line-possible satellite components weighing about 15 pounds (7 kilograms) each could be assembled in space.

Looking much like Legos, the components encapsulate such satellite aspects as power, sensors and thermal management. They could be assembled in different ways to accommodate different missions. A kind of satellite ala carte menu - pick and choose what you need and have it assembled right on the spot.

Another Phoenix approach is a Payload Orbital Delivery (POD) system that would standardize satellites and/or their components to take advantage of hosted payload opportunities offered by commercial satellites.

The payloads would be about 1.3 feet by 1.6 feet by 2.2 feet and weigh between approximately 150 and 220 pounds. The best part is that they would use standard interfaces to attach the POD to the host satellite and release it at the proper orbit.

Together, these concepts, combined with the GRS robotic in-orbit services platform, could become the new way to build and service satellites, both military and commercial,in geosynchronous orbit. They offer opportunities to:

change orbits while in GEO,

to inspect satellites as part of routine maintenance,

to troubleshoot problems and repair components or replace those that are worn out,

to salvage parts off satellites that have completed their lifespans and

to add or upgrade satellite capabilities.

The whole model of robotic in-orbit services could revolutionize the entire satellite industry and achieve the long-standing aim of replicating the terrestrial model of "assemble, repair, upgrade, reuse," but doing so at GEO orbit 36,000 kilometers over Earth.

Watch this video of Melroy's presentation to see it for yourself -- and don't forget to leave your comments below.